Calcutta: The season's densest fog stalled flight operations at the airport for more than an hour early on Tuesday, and the next two days might be just as trying for travellers, going by the weather forecast.
Four flights approaching the city had to be diverted and several more were forced to delay landing till visibility increased.
Airport officials said the secondary runway had been operational at night because the primary one, equipped with a CAT II instrument landing system, was under maintenance. The secondary runway has a CAT I system with a visibility limit of 550m.
Visibility had started dropping around 2am and was down to 50m within 10 minutes - the lowest for assisted landing with the airport's new CAT III-B system that won't be operational until January 4.
The first aircraft to be diverted on Tuesday was a Jet Airways flight from Bangalore that was to land at 2.35am. The aircraft was diverted to Nagpur. A SpiceJet flight each from Guwahati and Visakhapatnam were to land at 2.37am and 2.40am respectively, but both were diverted to Bhubaneswar.
Flight operations were later shifted to the primary runway, where the CAT II system allows assisted landing till a lower visibility limit of 350m. But visibility at that stage had barely increased to 250m, extending the wait.
By then, an IndiGo flight from Pune had to be diverted to Bhubaneswar. Sourav Ganguly and Abhishek Dalmiya, the joint secretary of the Cricket Association of Bengal, were on that flight. "Forced smile.. flight diverted to bhubaneshwar due to thick fog in kolkata. No idea when we would be returning to our original destination," Abhishek posted on Facebook around 4am.
IndiGo's flight from Bangkok and a Qatar Airways flight from Doha were unable to land either. Both hovered over the city till after 3.15am.
Trains delayed
Fog in north India delayed several trains to Howrah, including the Mumbai Mail, Jodhpur Express, Jammu Tawi Express and Amritsar Mail. Half a dozen local trains were delayed between 4am and 10am, Eastern Railway said.
